1. Field of the Invention
The invention relates to a base plate, for building devices for clamping workpieces in a defined and reproducible position, with grid points arranged at uniform coordinate spacings.
2. Description of the Related Art
European patent document 0 222 147 B1 shows a system for building devices including a base plate of the aforementioned kind on which the device of the system can be built. The base plate of this known system has fitting bores arranged at uniform coordinate spacings. The fitting bores provide the grid points which define the grid pattern spacing.
It is an object of the present invention to provide a base plate of the aforementioned kind which can be produced inexpensively without loss of precision and is as universally useable as possible.
In accordance with the present invention, this is achieved in that the grid points are formed in the shape of concave spherical depressions having center points positioned on crossing center lines arranged perpendicularly to one another and spaced by the grid pattern spacing, wherein the crossing center lines define the ideal base plate shape.
The mechanical machining of the base plate is thus limited substantially to the manufacture of the concave spherical depressions which are to be produced at one or both surfaces at the preset grid pattern spacing. The center points of the concave spherical depressions are not necessarily positioned at the physical surface of the base plate but on an xe2x80x9cideal surfacexe2x80x9d. When the actual shape of the base plate deviates from the ideal shape, and this is usually the case for unmachined cast aluminum, the center points are positioned always on the ideal shape and, accordingly, the concave spherical depressions also define the ideal shape. When these concave spherical depressions then are used as grid points for fastening connecting elements and other device modules, the attached components, for example, feet, are always built up starting at the ideal plate shape. The course and the design of the actual surface of the base plate thus do not have any effect. The center points of the concave spherical depressions are thus not positioned on the surface of the actual base plate, but located on its ideal shape. Accordingly, the surface of the spherical depression produced by machining can be differently sized.
According to an especially advantageous embodiment, the base plate, when viewed in a plan view, i.e., onto the clamping or mounting plane, is embodied as a uniform grid structure having diagonal grid rods extending at an angle of 45xc2x0 to the center lines extending through the center points of the spherical depressions. The center points of the spherical depressions are positioned respectively at the renter portions of the corresponding grid rods. The penetrations or voids between the grid rods have a uniform, preferably substantially square, cross-section.
This embodiment of a grid structure provides a very lightweight base plate which, however, maintains a high stiffness with respect to torsion and bending forces. This base plate can be produced especially economically as a cast aluminum member. A further machining step is not necessary or less machining is needed. Precise measurements of the base plate are not required because the required precision is provided by the spherical depressions and their center lines that are very precisely positioned on the ideal shape. The spherical depressions are provided at the center portions of the grid rods, optionally in a portion of the grid rods having a thicker cross-section, so that, the grid pattern spacing is maintained. The diagonal for a corresponding square base structure is always {square root over (2)}xc3x97 the grid spacing. The voids or penetrations have a substantially square cross-section which is compromised only by thicker center portions in the area of the concave spherical depressions and by the rod intersections (nods).
In an advantageous embodiment of the base plate with rod intersections (nods) of the diagonal grid rods, second concave spherical depressions are provided having center points positioned on the points of interception of the diagonals of the grid rods. In another preferred embodiment, the spherical depressions have fastening bores which extend perpendicularly to the crossing center lines and which are optionally provided with a thread.
The base plate may be divided, meaning that one large-size base plate is cut to smaller ones which are then combined to a larger base plate of a different size. The base plate in this embodiment is divided along a separating line, extending through the rod intersections of the diagonal grid rods, into two or more correspondingly smaller sized base plate portions. In the vertical separation surfaces (end faces) concave spherical depressions with fastening bores are provided. These individual base plate portions are then assembled to larger ones by means of interposed disc-shaped lenses with correspondingly embodied convex spherical sides and fastening screws. The effective thickness of the disc-shaped lenses corresponds to the thickness of the material removed from the base plate by the cutting process. The special design and connection employing disc-shaped lenses ensures that the grid pattern spacing is not disturbed upon combination of multiple base plate portions of smaller size. The material that has been removed during cutting is thus again added to the grid pattern spacing by the effective thickness of the disc-shaped lenses. The production of large base plates of different dimensions and shapes is thus possible by combining smaller sized base plate portions.
Especially advantageous is a base plate, with concave spherical depressions and optionally fastening bores, arranged preferably only on one side which forms the bottom side of the base plate in its position of use for fastening foot or connecting elements. The feet of the foot and connecting elements is matched to the (preferably square,) shape of the penetrations or voids and in one position can be pushed from the top side of the base plate through the base plate to the bottom side. The surface of the foot facing the bottom side is provided with convex spherical projections positioned relative to one another according to the grid pattern spacing and located at the ends of diagonals extending at a right angle to one another to the ends of the foot. The foot or connecting elements, after insertion and rotation about their axis by 45xc2x0 and snap-in connection of the convex spherical projections in the correlated concave spherical depressions, are secured by fastening means. This embodiment is especially useful where there is a risk that the surface of the base plate is subjected to high mechanical loads or soiling. In this case, the surface provided with concave spherical depressions is selected as the bottom side so that the unmachined side faces upwardly. The concave spherical depressions of the bottom side (after the base plate has been positioned upside down) are used for fastening foot and/or connecting elements by employing the grid pattern spacing of the spherical depressions. Feet of the foot or connecting elements are pushed through the penetrations or voids and, upon rotation, are then connected to the spherical depressions, in which position they are subsequently secured by suitable fastening means.
The base plate in its various embodiments, especially when embodied as a grid structure with diagonally extending grid rods, when combined of smaller base plate portions, or when provided with foot or connecting elements insertable through the voids of the grid structure and provided with convex spherical projections configured to match the concave spherical depressions as well as the grid pattern, can be used substantially universally in various ways based on the basic grid structure in combination with the concave spherical depressions. Of course, it also serves as a component of the system for building devices as disclosed above.